Fluid pressure instrument



April 1942- I w. o. bAvls v I 2,279,861"

FLUID PRESSURE INSTRUMENT Filed April 30, 1941 erated instruments of movements of a to the instrument.

7 slot it receiving one end of a link I5.

Fatented Apr. 14, 1942 UNWE ESTATES 2,279,861 FLUID PRESSURE DISTRUll/ENT to S. Smith 8; Sons ited, firicklewood, London,

company Application April Wilfred Gwen Davis, London, England, assignor (Motor Accessories) Lim- England, a British 30, 1941, Serial No. 391,203

lin Great Britain February 16, 1940 2 Claims.

This invention relates to fluid pressure opthe kind in which the fluid pressure operated flexible diaphragm are transmitted to an operating mechanism including an indicating or control member, for example, a pointer moving over a scale, and in which a limiting stop is provided and is engaged by a part of the operating mechexcessive movement of the in- If, however, the suddenly arrested anism to prevent dicating or control member. movement of the diaphragm is by the limiting stop, the mechanism is liable to be damaged and the object of the present invention is to overcome this difilcuity.

According to the present invention, there is provided a fiuid pressure operated instrument of the hind specified. wherein the operating mechanism comprises a lost between the diaphragm and that part of the mechanism which engages the limiting stop and a spring or other resilient means biassing the said part of the operating mechanism towards the limiting stop. When this arrangement with the limiting stop is engaged, the diaphragm is not suddenly arrested but is permitted to move with lost motion.

According to a further feature of the invention the resilient biassing means is connected between said part of the operating mechanism and a fixedabutment, so that when the limiting stop is engaged, the diaphragm can through the extent of the lost motion.

motion connection .3 move freely In a preferred construction the lost motion connection is provided between the diaphragm and a link connecting the diaphragm to a crank on a rockshait oi the operating mechanism, the movement of which shaft is restricted by the limiting stop and wherein the means consists of a spring connected at one end to the rockshaft and at the other end to the fixed abutment.

One application of the invention to a barometric altimeter is illustrated by way of example in the accompanying drawing, in which- Fdigure l is a cross-section of the instrument. an

Figures 2 and 3 are enlarged detailed views at right-angles to one another.

Referring to the drawing, the altimeter comprises coupled barometric capsules it, carried at one side on a pillar H, fixed to a frame I2 At the other side of the capsules there is a post l3 having a lengthwise This link'has a lengthwise slot l6, receiving a cross pin it fixed in the post I3. The other end of the link I5 is connected by a pivot l8 to a crank resilient biassing to be turned by the spring is fixed to a rockshaft 20, which is rotatably mounted in the frame [2. This rockshait is connectedby a linkage or gearing to one or more pointers in the usual manner. The movements of the rockshaft as a result of expansion of the capsules is limited by a stop and engaged by the crank iii. A coiled spring 22 is connected to one end of the rockshaft 2i) and at the other end to a post 23 on the frame it; The spring 22 is arranged rotationally to bias the shaft 2B the limiting stop 2!, thus holding the link G5 with the outer end of the slot E6 in engagement with the pin H, as shown in Figure 2. The movements of the post it, as a result of expansion of the capsules thus allows the rockshaft 22. The movements of the post l3 as a result of construction of the capsules turns the shaft 20 against the action of the spring 22. If excessive expansion of the capsules occurs to bring the rockshaft to its limiting position, the capsules can continueto expand by reason of the pin I! being permitted to travel along the slot 16 without any load to be provided on the mechanism. The mechanism is thus protected from damage which might result from such excessive expansion.

I claim:

l. A fluid pressure operated instrument comprising a flexible diaphragm, a diaphragm operated member, a transmission mechanism affording a positive driving connection from the flexible diaphragm to the said operated member, a limiting stop engaged by a part of said mechanism to restrict the motion thereof, said mechanism having a lost motion connection between said diaphragm and said part, resilient means biasing said part towards the said limiting stop and a fixed abutment for the resilient means, said resilient means being connected between said part and said fixed abutment.

2. A fluid pressure operated instrument comand resilient means connected between said fixed abutment and the rockshaft and biassing said rockshaft towards the position in which it is halted by said limiting stop. I

WILFRED OWENDAVIS.

2| on the frame it to urge the crank l9 towards 

